(PURPOSE ) The purpose of this study was to find relation between Matrix metalloproteinase (MMP) and arthroscopic findings in sheep TMJ osteoarthritis (OA).(MATERIALS AND METHOD) After TMJ OA was induced, synovial fluid was aspirated at 2, 4, 6, 8, 12 and 24 weeks postoperatively. The arthroscopic findings on the temporal surface were obtained just before sacrifice. The arthroscopic findings were classified into three stages. (Stage 1 : Fibrous surface without fibrillation. Stage 2 : Fibrillation of the surface layer. Stage 3 : Bone exposure.) TMJ OA was evaluated histopathologically. The histologic findings were classified into three stages, too. (Stage I : Smooth surface and even thickness of fibrous layer. Stage II : Uneven thickness of the surface layer. Stage III : Bone exposure.) MMP was detected using gelatin zymography.(RESULT) Pro MMP-2 was detected at 2, 4, 6, 8, 12 and 24 weeks. Activated form of MMP-2 was detected at 2 and 4 weeks postoperatively. According to the arthroscopy, 11, 7 and 2 joints were classified into Stage 1, 2 and 3, respectively. Histologically 14 and 6 joints were classified into Stage 1 and 2, respectively. TMJ destruction gradually progressed over time. Diagnostic accuracy of the arthroscopy was 80%, whereas overdiagnosis was 15% and underdiagnosis was 5%.(CONCLUSION) MMP-2 activity may be correlate with initial articular cartilage destruction rather than progressed stage of sheep TMJ OA.Pro MMP-2 is valuable as a marker in detecting early osteoarthritis. The arthroscopy is reliable for detecting TMJ OA.